1. Field of the Invention
The present invention relates to a spin-transfer magnetization reversal type magnetic random access memory (MRAM), and a method of manufacturing the same.
2. Description of the Related Art
A magnetic random access memory (MRAM) that uses magnetization reversal by the spin transfer method as a write operation is regarded as more advantageous than current magnetic field write in view of, e.g., micropatterning of cells and the prevention of a write error to an adjacent cell. A minimum processing dimension of lithography determines the area of a magnetic tunnel junction (MTJ) element used in this magnetic random access memory.
In spin-transfer write, however, the current density needed for magnetization reversal is as high as 1×107 A/cm2. This poses the big problem that the amount of electric current that must be supplied to the MTJ element is large for a practical use. Accordingly, the spin-transfer magnetization reversal type magnetic random access memory is required to realize an element area independent of a minimum processing dimension of lithography.
Note that pieces of prior art reference information relevant to the invention of this application are as follows.                [Patent reference 1] Jpn. Pat. Appln. KOKAI Publication No. 2004-259913        [Patent reference 2] Jpn. Pat. Appln. KOKAI Publication No. 2001-084758        [Patent reference 3] Jpn. Pat. Appln. KOKAI Publication No. 2004-139681        [Patent reference 4] Jpn. Pat. Appln. KOKAI Publication No. 2004-193479        [Patent reference 5] Jpn. Pat. Appln. KOKAI Publication No. 2003-273331        